Method and apparatus for increasing electronic emission



Dec. I8, '11923. 31,47768 H. P. DONLE METHOD AND APPARATUS .FOR INCREASING ELECTRONIC EMISSION Original Filed May 9, 1919 L@ ANS Jef la 2o /Waas Mawr/fu, nu rs.

Teatre@ nec. is, reas.

4"HAROLD r. noNLE,I orv MERIDEN, coNNnCIIcUn-'AssIGNoR To run CONNECTICUT TELEPHONE & ELECTRIC COMPANY, INCORPORATED, OF MERIDEN, CONNECTICUT,

LA. CORPORATION i01E CONNECTICUT. l

on AND APPARATUS FCR INCREASING ELECTRONIC RNIssIoN.-

Application led May 9, 1919, Serial No'. 295,897. Renewed August 16, 1923.-

To all whom'z't may concern:

Beit known that I, HAROLD P. DoNLE, a citizen of the United States of America,A

residing, at Meriden, Connecticut, have invented new and useful Methods and Apparatus for Increasing Electronic lijrnission,l

of which the-following is a specification.

The object of my present invention is to increase the electronic emission of a hot electrode4 or filamentary cathode.l I have discovered that when a material having a high temperature coefficient of resistivity', such as glass, is subjected to the action of 'electrolysis between two electrodes,

,the electronic emissivity of the cathode, as

the result of this treatment, is greatly increased.

-It appears that 'some of the elements or materialemitted during such disassociation are deposited on, or carried to, the filament cathode element and become a source of elec tronic emission, the actual cathode or filament -being the support for thiselectronic source. 4 Y,

This material which is deposited upon and retained at the filament cathode element is of such a nature that its emission at a given temperature is much greater than that of the supporting filament or cathode material, which may be of a metal such as' tungsten, molybdenum, etc.

For the sake of a more complete disclosure attention is directed to the accompanying drawing wherein, 1 have illustrated first a test form of apparatus and secondly, a commercial development of the invention.

More specificially, Figs. l, 2 and 3 illustrate a testing or demonstrating form of the tube, showing the connections for demonstrating the operation of the invention.

Fig. 4, is a graphic illustration of the results of such tests. I Fig. 5, is a more or less diagrammatic il lustration of a commercial use of the invention.

The tube Y illustrated in Figs. 1, 2 and 3, is shown provided with a neck 8 by which it is-connected with a vacuum pump, the latter not being illustrated. lt will be understood however, that any efiicient form of l high vacuum pump may be employed.

Within the tube are sealed the hot electrode, vwhich in thisl case is a metallic {ilain the form of a coating of silver, or the like,

applied directly to the glass wall of the tube. In the first test `Vthe filament was heated by a battery A, one side of which was connected with va variable source of potential B, the other terminal of this potential being connected in series with a micro-ammeter 12 to the electrode 10, which in this case acts as the anode. varied in steps by means of the adjustable resistance shunt 13 and readings of the anode current taken for different values of anode potential, the results of these/observations being plotted and indicated by'the curve ll in Fig, 4;. Tt will be seen that saturation occurred at lapproximately 5 volts with an anode current of 100 micro-amperes.

The next step consisted in disconnecting the inside anode 10-rom circuitand connecting the second battery B with4 the external electrode 11 by means of a connection 15. By these connections the external elec.-4 trode is made an anode and an electron discharge is created between the filament andv outside anode through the wall of the glass. This circuit was allowed to operate for'about five minutes. During this time I believe the action was that the passage of current from battery B to electrode 11, through the warmed glass wall 7 and across the evacuated on the inner wall and in the end portion of the tube as indicated at 16.' rlhis film has` the appearance and exhibits the characteristics of metallic sodium and so far as l have been able to ascertain up to the present time is in fact sodium in the metallic form. ln the course of this action a cert'ain amount of material is carried to and deposited upon the fllamentary electrode or cathode 9, as

The anode potential was is further demonstrated from the step which follows, .-noyvfbe described.

Indire ird'step of the test the outside anode is disconnected and the original conf gtionsrstored, as indicated in. Eig. 3,

. 1th-, `c'nimectiions ,the anode, potential isvaiiiy inthe same way'as in making the lirst partiof the test and the results plotted as before. 'Tha re1ues=-0btained areindicated b the curve 17 in Fig. 4. This curve shows t attimi-emission.fromfthe filamentis very greaqtly 4increased, and that at the same time 'the saturation voltage V is increased. The anode curi-ent at saturation isV shown tobe flmicraamperes. In other'words, thefelectronic emission, asl a result of the electronic'divscharge, has been increased in the ratio of Etwentyl to one 'During allj three steps.` of this test the vacuum-"pump was connected'with the tube and4 was; operated to maintain the highest possiblevacu-um within the' tube and to remove" 'any gases that might `exist. This renio'val'ot-whatever-gases' that may have existed'within theftube, did not however` aifect. the deposit ofthe metallic element within the tulp` Ffrm tests which I have .conductedlit appears that the increased'emission is not perm'anent Usually the` increased emission willffia'st for approximately ten minutes at the endof which tiinethefe'mission rate will fall`until'itdrops blaclr to the rate `which'is normal -forthemet'al which-.is employed, in other 'word,s,` 'thatrate 'represented Vfor instance bythe first curve (14)*.k

The increased 'electronic' emission may howeverbemairitained by continuously passl Vincurrent through' the wall'ofthef glass tu e, during the n'ornifal operationofthe tube.' Thus, as I'understand' it, renewing the deposit, upon the iiiamentarycathod'e-by the continuous or substantially continuous elec# trolytic dissociation", ot 'the current-carryixn glass and the -cnseguent provision -of sodium' ions for'this`purpos'e.- f

In" Fi`g.f 5 vIl have illustrated a foimof apparatus and 'shown a completedftube wherein this'result is accomplished In this illustration lthere is in laddition to the filainentand the anode within the tube, a controlling 4electrode or so-,called grid "18, the grid 'and'anode each consisting in this case ofian open spiral of wire surrounding the filament, fthe `grid'-being disposed within the anode', and-between' that and ythe lament.

An external electrodel or secondary anode 22, siiil'arto that first described, is provided, the saine being shown as bandlof silver, or other metal bf'like characteristicaiapplied directl-yto `the outer v vallA of the bulb.' The three elements of the tube are shown connected inV the usual way for detecting radio oscillations, the control electrode 18 'being shown connected with the antenna 19 and lstrates the .anode 10 being shown connected in the telephone circuit. 20, The .outs-ide electrode 22, which is provided inthis instance simply for the purpose of increasing and holding constant the electron flow., is shown connected through a .choke-coil 2l, ,with the posi` tive terminal of the B battery. This chokecoil is shown provided with an iron core so as tochoke back eflectricaloscillations and tlius: provides a means for producing and f maintaining a greatly increased electronic `emission and hence amore elicient instrument. l

While I have described the somewhat ohscure henomcna observed within these vacuum tu esin terms of electrolytic dissociation of the glass to produce a qu'antityot positive sodium ions which .are attracted lto the filamentary cathode and deposited thereon, and while this explanation is in full agreement 'with all the facts I have been able, to determine in long study of these actions, I do not wish to be bound by this particular theory. My discovery is eminently practical. and is not. limited in its useful applications byt-he theoretical analysis which I have attempted in the interest of clarity; I have found that. by the process described I can increase many-fold the electron-emitting ability of a cathode, without in any Way exposing it to the action of special minerals, etc.,fand without treating it (or mixing with it) prior to its mounting within the'vacuum tube yany materialsnot usual in filament manufacture. My inventiontherefore permits me" to secure greatly increased electron emission at an temperature from a standard cathodeor fi amentQo tungsten,'molybdeA num or the like, and consequently to secure the lfull equivalent of normal electron emission from such laments at temperatures far below normal.

The.- form of construction illustrated in Figs. 1 to 3 in which there is an unobstructed electron pat-h between the cathode 9 and the andel() is claimed in my application No. 616,660 iiled February 3rd, 1923. In said application I have also -broadly claimedV with resp'ect .'toi'vacuum tube signalling devices the use of metalssuch as sodium which can be derived fromthezwall ofthe tube for the purpose of increasing the electron emission of a highly refractory iilamentary cathode.

1. The method of increasing the eleciii() ditions to permit its ionization whenin operation.

20. The process of operating a'thermionic valve whic consists in passing a thermiomc l current between a filament and an anode located within the tube of said valve and simultaneously passing a thermionic current through the wall of said tubean'd between the lament Within thetube and a secondary anode at the outer surface of the tube.

21. Thev pross of operating a thermionic valve which consists in passing a thermionic current between a metallic iilament and an anode located within the tube of said valve and simultaneously passing a thermionic current through thewall of said tube and between the metallic filament within'the tube and a secondary anode at the outer surface of the tube.

22. An evacuated electron-tube containing a highly refractory iilamentary cathode, an anode, an auxiliary electrode, and a supply l of an alkali metal within said tube.

. 23. An evacuated electron-tube containing a highly refractory iilamentary cathode having a coating of analkali metal, an anode and an auxiliary electrode arranged to modify the field between said cathode and anode. 24, A vacuum tube having a cathode, an anode, and a third electrode and containing free'sodium., f y

25.. A vacuum-tube having a cathodehau anode, and a third electrode and containing a free alkali metal.

26. A 'vacuum tube having a cathode, an anode, a4 third electrode, and means for i supplying sodium ions within the tube.

2.7. A vacuum vtubehaving a cathode, an

refractory iilamentary cathode coated with anode, athird electrode, and means for 'supplying ions of an Aalkali metal within the nalling having an anode, a highl .refractory filamentary cathode coated wit 'an' alka metal, 'means for maintaining sfuchloo'atiii during operation of the tube and janauxi 2 iary input electrode. v

29. A vacuum tube device havinga highly an alkali metal, an anode, an-aiixil'iary elfec-l trode, a coating of an alkali metal o'n the vinner Wall of the tube, and means for renewing the coating on the cathode during opera` tion of the tube.

30. In a lfradio signalling system, a wave intercepting device, a vacuum. tube operatively connected therewith and having av highly refractory filamentary cathode, an anode and a third electrode, said tube containing free alkali metal, and a translating device operatively connected with said tube.

31. Ina radio signalling tube, a vhighly refractory iilamentary\ cathode of asingle' 

